Tough repair for spacewalkers today

May 16, 2009 5:35:44 PM PDT

CAPE CANAVERAL, Fla. --

Spacewalking astronauts gave the Hubble Space Telescope a more commanding view of the cosmos by installing a new high-tech instrument Saturday, then pulled off their toughest job yet: fixing a broken camera. It was the third spacewalk in as many days for the shuttle Atlantis crew and the most intricate ever performed because of the unprecedented camera repairs. Astronauts had never before tried to take apart a science instrument at the 19-year-old observatory.

Hubble's chief mechanic, John Grunsfeld, deftly opened up the burned-out camera and plucked out all four electronic cards that needed to be replaced.

"Somehow I don't think brain surgeons go 'woo-hoo' when they pull something out," one of the astronauts observed from inside Atlantis.

To everyone's surprise, the new cards and power supply pack went in just as smoothly. In fact, the astronauts found themselves running ahead of schedule for a change, their spacewalk lasting the allotted 6½ hours. The first two spacewalks ended up running long because of unexpected difficulties encountered with Hubble, last visited seven years ago.

The astronauts cheered when Mission Control radioed up the news that the repaired camera had passed the first round of testing.

"That's unbelievable," Grunsfeld said.

A second round of testing was expected to last well into the night. Early Saturday evening, Mission Control told astronauts that a new spectrograph that spacewalkers also installed passed both its tests. Atlantis crew responded with what has become customary whooping it up.

Even with two spacewalks remaining, including the repair of a major instrument Sunday, NASA managers were handing out accolades and talking about how improved the telescope already is.

"At this point in time, Hubble has reached a new high in terms of its capability," Hubble program manager Preston Burch said at a news conference Saturday afternoon. "We're enjoying the moment and savoring it."

Atlantis' crew broke out in grins.

In a video sent to Earth taken before the spacewalk, Mike Massimino, who spacewalked Friday and will do so again Sunday, compared dealing with Hubble to a heavyweight fight. But he also was looking like the winner in such a bout.

"We don't warranty any of the work," Massimino joked for the camera in a heavy New York accent. "Labor's not guaranteed."

The high-stakes job unfolded 350 miles above Earth. Orbiting so high put Atlantis and its astronauts at an increased risk of being hit by space junk. NASA had another shuttle on launch standby in case a rescue was needed.

Earlier, Grunsfeld and his spacewalking partner, Andrew Feustel, accomplished their first task, hooking up the $88 million Cosmic Origins Spectrograph.

They made room for the new supersensitive spectrograph - designed to detect faint light from faraway quasars - by removing the corrective lenses that restored Hubble's vision in 1993.

"This is really pretty historic," Grunsfeld said as he and Feustel hoisted out the phone booth-size box containing Hubble's old contacts.

Hubble was launched in 1990 with a flawed mirror that left it nearsighted. But the newer science instruments have corrective lenses built in, making the 1993 contacts unnecessary. The latest addition, the cosmic spectrograph, is expected to provide greater insight into how planets, stars and galaxies formed.

The switch - taking out the 7-foot-long box containing the corrective lenses and putting in the spectrograph - proved straightforward. It's exactly the kind of replacement work astronauts performed on four previous repair missions.

Fixing the 7-year-old camera was far more complicated. The instrument - called the Advanced Camera for Surveys - suffered an electrical short and stopped working two years ago. Ground controllers had been able to eke out a minimal amount of science but wanted it back in full operation.

Before it broke, the surveys camera provided astronomers with the deepest view of the universe in visible light, going back in time 13 billion years.

NASA considered this repair job - and one planned Sunday on another failed science instrument - to be the most delicate and difficult ever attempted in orbit. Neither instrument was designed to be handled by astronauts wearing thick, stiff gloves.

Grunsfeld unscrewed 32 fasteners to reach the camera's electronic guts, all the while working around a corner that prevented him from seeing everything he was doing. He used long tools designed just for the job - and got it done faster than planned.

NASA hopes to keep Hubble working for another five to 10 years.

Already, the astronauts have given Hubble two top-of-the-line science instruments, fresh batteries and gyroscopes, and a new science data unit.

If all goes well, the final spacewalk is set for Monday and the telescope will be released Tuesday from Atlantis.